Wax esters or fat esters have a wide range of applications as lubricants, polishes, plasticizers, antifoaming agents, coating materials in different industries. Particularly in cosmetics, wax esters are formulated with other ingredient in the delivery system, preferably in an emulsion form, to cater aesthetic effect to the user upon applying the formulated emulsion. Emulsions are mixtures of two insoluble materials containing water and oil phase which are stabilized against separation using emulsifier (surfactant). Emulsions are defined as heterogeneous systems in which at least one immiscible or barely miscible liquid is disperse in another liquid in the faun of tiny droplets of various sizes.
In an emulsion while on storage, several breakdown processes may occur such as creaming, sedimentation and flocculation. To avoid or slow the breakdown process, the emulsion formed is preferably in the isotropic state. Thus, choosing the right emulsifier or other stabilizing agent is crucial. Study of emulsion stability in systems with comparable amounts of oil and water, with low nonionic surfactant content have shown the strong correlation between the phase inversion phenomenon and the existence of three isotropic phase equilibria with low or ultra low interfacial tensions. The surfactant phase is then the very microemulsion domain, which is the stable state of these oil/water mixtures in the presence of a small surfactant amount. An accurate determination of the hydrophilic-lipophilic nature of surfactants plays an essential role in guiding the formulation of microemulsion. Nonetheless, fat esters of various source contains carbon chains of different length which, possibly, only react with certain type of emulsifier or stabilizing agent to achieve the isotropic state.
Emulsions containing illipe-based fat esters have their own specialty. Illipe is the name of tree that comes from the genus of ‘shorea’. Illipe fat can be obtained from the seed and it is also known as illipe butter. Illipe butter is classified as exotic butter that can moisturizes the skin and restores elasticity. It also can prevent dry skin, the development of wrinkles and reduce degeneration of skin cells. Illipe fat esters were produces by reaction oleyl alcohol and illipe fat. Thus far, no work is being devoted to develop an isotropic and homogenous milky emulsions system based on illipe fat esters.